API 571 Certification (Corrosion & Materials) Practice Test

Which type of cracking is a concern for all engineering alloys?

1. Hydrogen embrittlement

2. Mechanical fatigue

3. Polythionic acid SCC

4. Liquid metal embrittlement

The correct answer is: Mechanical fatigue

Mechanical fatigue is a primary concern for all engineering alloys because it represents the failure of a material due to repeated cycles of stress or loading over time. Fatigue occurs when a material is subjected to a fluctuating load, even when that load is below the material's yield strength. This type of cracking can lead to the progressive and rapid deterioration of material performance, ultimately resulting in failure. Unlike other forms of cracking that may be specific to certain environments or conditions, mechanical fatigue can affect a wide range of metals and alloys regardless of their specific composition. Factors such as loading conditions, environmental influences, and cyclic stress can influence the fatigue behavior of any engineering alloy. Hydrogen embrittlement, polythionic acid stress corrosion cracking, and liquid metal embrittlement are either specific to certain environments or procedural conditions, meaning they do not universally impact all engineering alloys. Therefore, while they are important concerns, they do not have the same general applicability across all materials as mechanical fatigue does.